Caffeine's Effect on Women's Estrogen Levels Varies by Race

In a study measuring the effects of 200 milligrams caffeine – - about two cups of coffee - on estrogen levels in women of child bearing age by race, researchers found slightly reduced levels of estrogen in white women and comparatively elevated levels in Asian women.

While black who consumed 200 milligrams or more of caffeine a day had elevated estrogen levels, the result was not statistically significant.

Caffeinated soda and green tea intakes were linked with increased concentrations among all races.

The study involved 259 participants who were followed for up to 2 menstrual cycles and provided multiple blood specimens for hormonal assessments in every cycle.

The study was led by Karen Schliep of the Eunice Kennedy Shriver National Institute of Child Health and Human Development and was published in the January edition of The American Journal of Clinical Nutrition.

"Short term, these variations in estrogen levels among different groups do not appear to have any pronounced effects," said Enrique Schisterman, Ph.D., at the Institute in statement released by the National Institutes of Health.

Schisterman said variations in estrogen level are associated with such disorders as endometriosis, osteoporosis, and endometrial, breast, and ovarian cancers.

“Because long term caffeine consumption has the potential to influence estrogen levels over a long period of time, it makes sense to take caffeine consumption into account when designing studies to understand these disorders,” he said.

Researchers said further research is needed to find the association between caffeine and caffeinated beverages and reproductive hormones and whether those relations differ by race.